Tensioners for safety belts must be constructed to be as small as possible due to the small amount of space available in the vehicle. Inside or outside the cylinder, a damping means is usually provided, influencing the axial length of the tensioner in a negative manner, which damping means brakes the piston at the end of the tensioning path and in so doing absorbs energy, whereby stress peaks are reduced. Owing to the length of tensioning path and damping path which were necessary hitherto, known tensioners have such an axial overall length that they can not be installed in the vehicle without cable deflectors.
U.S. Pat. No. 4,458,921 discloses a generic tensioner having a damping member in the form of a sleeve which surrounds the traction cable and adjoins a deflector fitting connected to the traction cable. At the end of the tensioning process, this damping part cuts into a sealing member provided on the end face in the cylinder end wall and is caught therein. This process serves for the damping at the end of the tensioning path. However, the damping path is extremely short by design, so that great stresses occur during damping.